﻿#define _CRT_SECURE_NO_WARNINGS 1

//编程初学者入门训练第七十题
//BC72 平均身高
//https://www.nowcoder.com/practice/b0e489a749f448e2b37f26ef56a76e58?tpId=107&tqId=33353&rp=1&ru=/exam/oj/ta&qru=/exam/oj/ta&sourceUrl=%2Fexam%2Foj%2Fta%3Fpage%3D2%26tpId%3D107%26type%3D107&difficulty=undefined&judgeStatus=undefined&tags=&title=

#include <stdio.h>

int main() {
    double n = 0.0;
    double sum = 0.0;
    while (scanf("%lf", &n) != EOF) {
        sum += n;
    }
    printf("%.2lf", sum / 5.0);
    return 0;
}